فهرست مطالب

  • Volume:8 Issue:4, 2011
  • تاریخ انتشار: 1390/09/19
  • تعداد عناوین: 29
  • L. Tan, Y. Long, F. Jiao, X. Chen Page 889
    A new chiral separation technology, aqueous two-phase extraction, was proposed for the separation of racemic mandelic acid. The distribution behavior of mandelic acid enantiomers was investigated in aqueous two-phase systems composed of polyethylene glycol and ammonium sulfate containing β-cyclodextrin as chiral selector. The influences of the pH, the mass fraction of polyethylene glycol and ammonium sulfate, the polymerization degree of polyethylene glycol, the initial concentration of β-cyclodextrin, mandelic acid enantiomers and extractive temperature on the distribution behavior were studied respectively. The results show that β-cyclodextrin is inclined to recognize L-enantiomer; under the optimized conditions, the separation factor reaches 2.46 and the enantiomeric excess is 42.13% in the top phase and 40.43% in the bottom phase, respectively. Aqueous two phase chiral-extraction with strong chiral separation ability, plays great role in preparative separation of racemic compounds and is important for the development of aqueous two phase extraction technique.
  • S. Khan, T.G. Kazi, J.A. Baig, N.F. Kolachi, H.I. Afridi, S. Kumar, A.Q. Shah, G.A. Kandhro Page 897
    Cloud point extraction (CPE) and solid phase extraction (SPE) methods were developed for the determination of µg l-1 of vanadium ions in surface, tap and bottled mineral water samples, based on the rapid reaction of vanadium(V) with 8-hydroxyquinoline (8-quinolinol) at pH 3-5. Both the sensitive extraction methods were successfully employed for the preconcentration of V in real samples. For CPE, V complexed with 8-quinolinol and then was entrapped in non-ionic surfactant Triton X-114, while for SPE, V was adsorbed on XAD -2 impregnated with 8-quinolinol. The experimental conditions for SPE (pH, eluent, and contact time between the liquid sample and the resin) and CPE (pH of sample solution, concentration of 8-quinolinol and Triton X-114, equilibration temperature and time period for shaking) were investigated in detail. The validity of SPE/CPE of V was checked by certified reference material of water (SRM-1643e). The extracted surfactant-rich phase (200 µl) was mixed with 200 µl of HNO3 in ethanol and this final volume was injected into electrothermal atomic absorption spectrometry with different modifiers. Under these conditions, the preconcentration of 25 ml sample solution allowed the raising of an enrichment factor of 100 and 10 folds for CPE and SPE, respectively. The concentration of V in surface water (river and lake), tap water and bottled mineral water samples was found to be in the range of 1.30-19.9, 1.05-5.25 and 0.67-1.21 µg l-1, respectively.
  • A. Ebrahimi, M. Habibi-Khorassani, S. Bazzi Page 908
    The effects of structural parameters and intramolecular interactions on N-glycosidic bond length in 3-methyl-2'-deoxyadenosine (3MDA) and 2'-deoxyadenosine (DA) were investigated employing quantum mechanical methods. All calculations were performed at B3LYP/6-311++G** level in the gas phase. The N-glycosidic bond length strongly depends on sugar configuration; it is shorter in syn conformation relative to anti in many cases where they have the same sugar ring configuration. The sugar conformation can influence the N-glycosidic bond through interaction with the O4' atom. The impact of intramolecular improper hydrogen bonds and H-H bonding interactions on N-glycosidic bond length was investigated in DA and 3MDA and their modeled structures. Improper hydrogen bonds decrease N-glycosidic bond length while H-H bonding interactions increase it.
  • M. Ghadermazia, F. Manteghib, S. Mehdizadeha, N. Kakaeia, A. Shokrollahic, Z. Malekhosseinic, M. Shamsipurd Page 919
    The new compounds, (phhyH)2(pydc), 1 and (phhyH)[Ni(pydc)(pydcH)].3H2O, 2, phhy: phenylhydrazine, pydcH2: pyridine-2,6-dicarboxylic acid, were synthesized and characterized by IR, 1H NMR, 13C NMR and UV spectroscopy. The structure of 2 was determined by X-ray crystallography. In the crystal structure, the metal ion was six coordinated by two tridentate (pydc)2- and (pydcH)- groups and each anionic complex unit, [Ni(pydc)(pydcH)]- was accompanied by one (phhyH)+ as counter ion and two water molecules. In compound 2, a large number of O-H∙∙∙O, N-H∙∙∙O and C-H∙∙∙O hydrogen bonds were observed. These interactions as well as other noncovalent interactions such as ion pairing, C-O∙∙∙π and π-π stacking play an important role in the formation and stabilization of the crystal lattice. In the solution study, the equilibrium constants for the binary pydc-phhy proton transfer system, the stoichiometry and stability of complexation of this system with Ni2+ ion in aqueous solution were investigated using potentiometric pH titration method. The stoichiometry of the most abundant species in the solution was compared to the crystalline cited metal ion complexes.
  • R.A.K. Rao, S. Ikram, J. Ahmad Page 931
    The ability of polystyrene-alumina-activated carbon composite as a synthetic adsorbent was investigated for the removal of Pb(II) ions from aqueous solutions. Various physico-chemical parameters such as pH, initial metal ion concentration, adsorbent dosage and contact time were studied. The optimum solution pH for the maximum adsorption of Pb(II) was found to be 4. Kinetic data were best described by pseudo-second-order model. The adsorption process followed both Langmuir and Freundlich adsorption isotherms at 30 °C. Thermodynamic studies indicated that the adsorption was spontaneous and endothermic in nature. Desorption studies were carried out by batch and column operations and it was found that 97% Pb(II) could be recovered by the column process using 0.1 M HCl as eluent.
  • M. Mahmoudiab., M.A. Shokrgozara, S. Bonakdara, M.K. Moghadama, S. Laurentc Page 944
    Superparamagnetic iron oxide nanoparticles (SPIONs) are being increasingly used in various biomedical processes such as hyperthermia, cell and protein separation, enhancing resolution of magnetic resonance imaging and drug delivery. Here, SPIONs were prepared by optimized co-precipitation of iron chlorides in basic medium and then coated with gold. Bare SPIONs and Au-coated SPIONs were characterized by TEM before incubation with fetal bovine serum for 0.5, 1, 2, 4, 8 and 24 h. After these interaction times, the mixture was deposed on a small column in a strong magnetic field (MACS�®system). The SPIONs were retained; different washing fractions were collected and studied by UV-Vis spectroscopy and by 1D gel electrophoresis. The study revealed the presence of proteins in the washing solutions and confirmed the strong interaction of the protein with the SPIONs.
  • N. Pourreza, A. Mouradzadegun, S. Mohammadi Page 951
    A new solid phase extraction method for the separation and determination of zirconium using agar as an adsorbent is described. The method is based on the adsorption of zirconium as arsenazo(III) complex on agar in a mini-column, elution with sulfuric acid-acetone mixture and determination by spectrophotometry. The effect of different parameters such as pH, concentration of the reagent, eluting reagent, and volume of the sample, amount of the adsorbent and interfering ions was investigated. The calibration graph was linear in the range of 5-300 ng ml-1 of zirconium under optimum conditions. The limit of detection based on 3Sb was 1.3 ng ml-1 and the relative standard deviation (R.S.D) for ten replicate measurements of 15 and 200 ng ml-1of zirconium was 3.7 and 1.8%, respectively. The method was applied to the determination of zirconium in water and soil samples.
  • A. Moghimia, H.R. Khavassib, A.H. Benvidic, M. Vojdanic, N. Faghihimoghaddamc Page 958
    Synthesis of two salts involving CH2O spacer between the imidazole nitrogen and hexafluoroisopropyl group in the fluorous imidazolium cations is reported. Such an insertion would result in the formation of a-ammonium ether. The two fluorous imidazolium salts involve one or two -CH2OCH(CF3)2 groups attached to the imidazole nitrogen atoms. These products were synthesized from the reaction between methyimidazole and imidazole as nucleophiles and sevochlorane, ClCH2OCH(CF3)2, as electrophile, in different molar ratios. The resulting products have been characterized by 1H, 13C, and 19F NMR and FTIR spectroscopy. Also, the single crystal X-ray diffraction analysis for the symmetrically substituted imidazolium product is presented. The preliminary animal tests indicated no anesthetic property but the two tested salts were found to behave as calmative.
  • J.J. Wanga, G.F. Hanb, Y.K. Shimc Page 965
    The synthesis of chlorins bearing 6C-straight chain was accomplished from methyl pheophorbide-a. A series of chemical modifications were employed for the construction of active functional groups, such as bromine atom or aldehyde group, on the periphery of chlorins. These functionalized chlorins further reacted with the reagent containing straight carbon-chain by common chemical reactions to produce target compounds. The structures of all new chlorins were characterized by elemental analysis, IR, UV-Vis and 1H NMR spectra.
  • A. Barzegara (Md) Davarib, N. Chaparzadehc, N. Zarghamid, J.Z. Pedersene, S. Incerpif, L. Sasog, A.A. Moosavi-Movahedih Page 973
    The development of antioxidants as useful drugs for the treatment of neurodegenerative diseases such as Alzheimer's is extremely challenging in medicinal chemistry. Coumarins have attracted great attention as possible therapeutic tools against oxygen radicals in human degenerative diseases. In order to establish the possible structure-antioxidant activity relationship, a series of twenty four 4-methylcoumarin derivatives were examined by employing reducing power measurements, and comparison with bond dissociation enthalpy and ionization potential calculations. Based on the reducing potency of 4-methylcoumarin derivatives with respect to trolox, these compounds were classified into five groups as “most active”, “more active”, “moderately active”, “less active” and “inactive” derivatives. The presence of hydroxyl groups is an essential requirement for the activity, and substitution of hydroxyl groups by methoxy groups leads to non-active derivatives. The results revealed that dihydroxyl groups in the ortho position show a better antioxidant activity with respect to dihydroxyl groups in the meta position. This is ascribed to the ability to construct more stable 4-methylcoumarin radical intermediates by rearrangement of intra-molecular hydrogen bonding. Our findings indicate that other important factors to enhance the antioxidant activity of coumarins are the number of hydroxyl groups, the presence of ester substitutions and a thiono functional group on the pyrone ring. However, bond dissociation enthalpy and ionization potential calculations alone are not sufficient to identify the best antioxidant structures. As a result, chemical and functional properties of molecules such as 4-methylcoumarins should be examined as a whole entity, considering all substitutions versus a single substitution to design functional compounds with good antioxidant activity.
  • A. Jamaliana, R. Mirib, O. Firuzib, M. Aminib, A.A. Moosavi-Movahedic, A. Shafieea Page 983
    A series of novel imidazolyl derivatives of fully and partially hydrogenated 1,8-acridinediones were synthesized and assessed for their cytotoxic activity on four different human cancer cell lines (HeLa, MCF-7, LS-180, and Raji cells). Although being inactive on LS-180 and Raji cell lines, the compounds showed weak to moderate anti-tumor activities on other cell lines and their IC50 ranged from 31.7 to more than 100 µM. Among the synthesized compounds 12b, 13b, 12c and 13c, bearing an electron-attracting substituent on the imidazole ring, and 12f and 13f, with a benzyl substituent, showed higher activities. Furthermore, the calcium channel antagonist activity of the derivatives, an undesired effect when these compounds are used as anti-tumor agents, was much lower than that of Nifedipine, a reference antagonist. Imidazolyl derivatives of 1,8-acridinedione represent an interesting template, showing promising biological properties. Further investigation on this chemical scaffold could potentially lead to the discovery of cytotoxic agents with low calcium channel blocking activity.
  • H. Aghabozorga, N. Firoozia, L. Roshana, H. Eshtiagh-Hosseinib, A.R. Salimib, M. Mirzaeib, M. Ghanbaric, M. Shamsipurc, M. Ghadermazid Page 992
    A novel supramolecular structure of an s-Block metal ion, Ca(II) atom, formulated as (pnH2)2[Ca2(H2O)2(Hhypydc)4]·4H2O (1), was synthesized and characterized by elemental analysis, IR, 1H and 13C NMR spectroscopies and single crystal X-ray diffraction. Compound 1is a member of a large family of supramolecular metallic compounds recently derived from a proton transfer ion pair,(pnH2)(Hhypydc), where pn is propane-1,3-diamine and (Hhypydc)2- is 4-hydroxypyridine-2,6-dicarboxylate ion. Based upon the molecular structure analysis of the binuclear anionic complex, the coordination environment around each Ca(II) atom is pentagonal bipyramidal with seven-coordination number. The strong hydrogen bonding between hydroxyl groups of two neighboring anionic complexes produce the nice tape as X-like supramolecular structure. Optimization was carried out using two standard basis sets of 6-31G (d,p) for the single anionic complex (S) and LanL2MB basis set for the double anionic complexes (D) which describe the electrons of all atoms. As an interesting finding from our theoretical calculations, when we reoptimized the double complexes in the presence of strong hydrogen bond interaction between two hydroxyl groups, O3-H3A···O8ii (ii = x-1, y, z-1), it was revealed that the parallel position of ligands to each other was exactly like that of the solid state. The complexation reaction of H3hypydc with Ca2+in aqueous solution was investigated by potentiometric pH titrations, the equilibrium constants and species distribution in various pHs. The for major complexes formed are described.
  • D. Azarifar, K. Khosravi Page 1006
    AlCl3.6H2O was explored as an efficient catalyst for the synthesis of gem-dihydroperoxides (DHPs) from ketones and aldehydes. The reactions took place within a short period of time using (30%) aqueous H2O2 as a “green” oxidant in acetonitrile under neutral conditions at room temperature to afford the products in high yields.
  • A. Tarassoli, B. Nekoeishahraki Page 1014
    The reaction between hexachlorocyclotriphosphazenes (N3P3Cl6) and three equivalents of bis-salicylidene ethylene diamine (HOC6H4-CH=N-CH2-)2 (salen) was investigated in two different experimental conditions. In the presence of anhydrous Na2CO3 in stirring tetrahydrofuran (THF) medium, the reaction led to a 50:50 mixture of tris[bis(salicylidene)ethylenediamine] cyclotriphosphazene, spiro-N3P3[(OC6H4-CH=N-CH2-)2]3 (1) and ansa (2) fully substituted products, whereas, in toluene solution, N3P3Cl6 with salen (3) and Al2O3/KOH afforded the spiro (1), as the only isolable compound. The spectroscopic data revealed that the oxygen atoms of salen moieties were selectively bonded to the three phosphorus atoms of the phosphazene ring. The new derivatives of cyclotriphosphazenes were characterized by IR spectrophotometry 1H NMR, 31P NMR spectral data and elemental analysis.
  • M. Moghadama, V. Mirkhania, S. Tangestaninejada, I. Mohammadpoor-Baltorka, H. Kargarb, I. Sheikhshoaeic, M. Hatefid Page 1019
    In this paper, highly efficient epoxidation of alkenes catalyzed by ruthenium(III) salophen chloride, [Ru(salophen)Cl], supported on functionalized chloromethylated polystyrene, PS, is reported. The PS was modified with 1,4-diaminobenzene, 4-aminophenol and 4-aminothiophenol, and [Ru(salophen)Cl] was attached to the supports via axial ligation. The prepared catalysts were used for efficient epoxidation of alkenes with NaIO4 at room temperature. These new heterogenized catalysts were characterized by elemental analysis, FT-IR spectroscopy, scanning electron microscopy and transmission electron microscopy. The heterogeneous catalysts were reusable in the oxidation reactions and were reused several times.
  • I. Yavari, S. Beheshti Page 1030
    ZnO nanoparticles were prepared and applied as a favorable catalyst in three-component one-pot cyclocondensation reaction of isatoic anhydride with amines and aldehydes to afford the corresponding 2,3-disubstituted quinalolin-4(1H)-ones in good yields. Reactions occurred under solvent-free conditions in high atom economy.
  • M. Khoobia, A. Ramazania, A.R. Foroumadib, H. Hamadic, Z. Hojjatia, A. Shafieeb Page 1036
    Heteropoly acids are reported as efficient catalysts for the microwave-assisted synthesis of 3-benzothiazolo and 3-benzothiazolino coumarin from o-aminothiophenol derivatives with 3-acetly and 3-cyanochromen-2-one in good to excellent isolated yields (73-95%). This study suggests new techniques for the synthesis of chromene derivatives using an inexpensive and easily available catalyst, a simple procedure, short reaction time, and good to excellent yields of the products.
  • H. Sun, L. Wei, Y. Zuo, Y. Wu Page 1043
    Gatifloxacin (GAFX), P-aminomethylbezoic acid (PAMBA), cefazolin (CFZL) and cefminox (CMNX) can be combined and administered perorally or intravenously, and are excreted mainly into the urine. A novel capillary zone electrophoresis (CZE) method was developed, for the first time, for an effective separation and simultaneous determination of the said four drugs in human urine. The electrophoresis conditions were investigated and optimized. A 25 mM borate buffer (pH 9.2) was used and the peak area was determined with UV detection. Under optimal conditions, the four drugs can be separated effectively. Good linearity was achieved with the correlation coefficients (r2) of > 0.999. The limit of detection (LOD) for PAMBA, GAFX, CFZL and CMNX was 5.8, 3.9, 7.8 and 15.0 μg ml-1, respectively. Their average recovery in human urine was 93.2, 98.3, 108 and 92.7%, respectively, with the RSDs ranging from 1.0% to 3.5%. The proposed method is simple, rapid and accurate, and provides the sensitivity and linearity necessary for the selective and simultaneous analysis of the test drugs in human urine at clinically relevant concentrations.
  • D. Shahabi, M.A. Amrollahi, A.A. Jafari Page 1052
    The oxidative conversion of 1,4-dihydropyridines to give the corresponding pyridine derivatives in excellent yields was easily effected using the catalytic amount of NaI in combination with H2O2 (30%) as a green external oxidant. The process is highly green wherein the solid products are easily filtered out after the addition of ice-water to the reaction mixture. This non-transition metal catalyst is cost-effective, affords simple work-up and easy separation of the product.
  • M.A. Zolfigola, A. Khazaei, E. Kolvarib, N. Koukabia, M. Gilandousta Page 1058
    The use of chlorine bleach (5% NaOCl) for the halogenation-oxidation of oximes to gem-chloronitro compounds is reported. Chlorine bleach afforded satisfactory yields when employed alone either at room temperature or under ultrasonic irradiation.
  • N. Bahrami Adeh, T. Afghani, M. Shamsipur Page 1063
    The morphology of plasticized sulfur with styrene (STY) and dicyclopentadiene (DCPD) was studied using scanning electron microscopy, to investigate the influence of type of additive and time on the rate of conversion of β- to α-structure. The results revealed that major part of plasticized sulfur with STY converted to α-phase after 30 days. While the DCPD-plasticized sulfur mostly possessed a β-structure and only a minor part was converted to α-structure with the elapse of time. The thermal behavior of sulfur, molten sulfur, and the plasticized sulfur samples were studied by thermogravimetry (TG) and differential scanning calorimetry (DSC), 522 days after their preparation. The results clearly revealed that, among different samples studied, the DCPD-plasticized sulfur possesses the highest thermal stability. The effect of addition of micro- and nanosilica, as modifiers, on the morphology and thermal behavior of the STY-plasticized sulfur was also studied. It was found that the presence of the above fillers to the matrix of STY-plasticized sulfur not only caused the creation of some cracks in the sample, but also could not block the conversation of β- to α-structure.
  • M. Asadia, G. Absalana, A. Zamanpoura Page 1073
    New complexes of Co(II), Ni(II), Cu(II) and Zn(II) with four new tetraaza Schiff base ligands, N,N'-bis(2-quinolylmethylidene)-1,2-ethanediimino (L1), N,N'-bis(2-quinolylmethylidene)-1,2-propanediimino (L2), N,N'-bis(2-quinolylmethylidene)-1,3-propanediimino (L3), N,N'-bis(2-quinolylmethylidene)-4-nitro-1,2-phenylenediimine (L4), were synthesized and characterized by elemental analysis, IR, 1H NMR, and UV-Vis spectroscopy. The thermodynamic formation constants of the complexes were measured spectrophotometrically, at the constant ionic strength 0.1 M (NaClO4), at 25 °C in MeOH solvent. The trend of the complex formation of a given metal ion with the ligands was found to be as follows L2 > L1 > L3 > L4 and the trend of a given ligand with the metal ions was Co(II) > Ni(II) > Cu(II) > Zn(II).
  • A. Ghorbani-Choghamarani, G. Azadi Page 1082
    Polyvinylpolypyrrolidone-supported hydrogen peroxide (PVP-H2O2), silica sulfuric acid (SiO2OSO3H) and catalytic amounts of ammonium bromide (NH4Br) are introduced as green media for the in situ generation of bromoniume ion (Br+), which was applied for the selective oxidation of sulfides and alcohols into sulfoxides and carbonyl compounds, respectively. The oxidation reactions were carried out heterogeneously in acetonitrile, as solvent, at room temperature (oxidation of sulfides) and/or 60 °C (oxidation of alcohols).
  • A. Yari, M. Dinarvand Page 1091
    Bromopyrogallol red (BPR) pH-indicator was incorporated into a sol-gel silica matrix and used for sensing pH as a solid indicator. Entrapment of BPR into silica matrix was performed by the acid-catalyzed sol-gel reaction of tetraethylorthosilicate (TEOS) and the BPR indicator. The immobilized BPR shows better behavior than its solvated form in solution. No leaching was observed during the repetitive experiments, indicating that BPR molecules were strongly trapped into the silica matrix. At optimal condition, the sensor responded rapidly to pH changes in a range of 2.33-9.42 with the response time about a minute. The equation A = 0.081 + 0.038 pH with R2 = 0.992 was obtained by regression of linear portion of the calibration curve plot of the sensor responses at various pH values. This sensor was highly sensitive, quite reversible and had a long lifetime of over 10 months.
  • A. Jamaliana, A. Shafieeab., B. Hemmateenejadc, M. Khoshneviszadeha, R. Miricd., A. Madadkar-Sobhanie, S.Z. Bathaief, A.A. Moosavi-Movahedie Page 1098
    The effect of twelve novel imidazolyl derivatives of 1,8-acridinedione (ligands) on calf thymus DNA was studied applying different biophysical techniques including UV-Vis spectrophotometry, CD spectropolarimetry and fluorimetric methods to gain deeper insights into the mechanism of interaction of the ligands with DNA. The binding parameters such as C50, Kapp, ΔGo(H2O) and m-value, followed by Scatchard analysis, indicate that among the tested ligands, four compounds; 12b, 13b, 12f and 13f, containing nitro and benzyl imidazole substituents, revealed uncompetitive intercalative mode of interaction with DNA. UV-Vis studies imply that the compounds bind cooperatively to DNA at the concentration range of 100-200 μM. Based on biophysical data, QSAR analysis, and docking simulations, we propose that in cytotoxic 1,8-acridinediones, the imidazole moiety is essential for pharmacological activity and the introduction of more flexible and electron-withdrawing substituents on the imidazole ring serves to enhance their DNA intercalating ability.
  • H. Khajehsharifi, E. Pourbasheer Page 1113
    The simultaneous determination of xanthine (XA), hypoxanthine (HXA) and uric acid (UA) mixture using spectrophotometric methods is a difficult task in analytical chemistry because of the spectral interferences. Partial least squares (PLS) modeling, as a powerful multivariate statistical tool, were applied to the spectrophotometric simultaneous determination of these substances. The concentration ranges for XA, HXA and UA were 3.0-24.3, 2.7-19.0 and 3.4-25.2 μg ml-1, respectively. The experimental calibration set consisted of 21 sample solutions with a mixture design for three-component mixtures. The absorption spectra were recorded from 220 to 320 nm. After orthogonal signal correction (OSC), the unrelated information was removed and the results were proved. The root mean square error of prediction (RMSEP) for xanthine, hypoxanthine and uric acid with OSC were 0.5161, 0.2997 and 0.5739 and without OSC were 1.6087, 0.8580 and 1.4009, respectively. This process afforded the simultaneous determination of XA, HXA and UA in human urine and human serum.
  • H.R. Shaterian, M. Ranjbar, K. Azizi Page 1120
    Brønsted acidic ionic liquid, triphenyl(propyl-3-sulphonyl)phosphonium toluenesulfonate, has been used as an efficient and reusable catalyst for the one-pot synthesis of 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles under solvent-free conditions in excellent yields.
  • M. Rahimizadeh, M. Bakavolia, Z. Gordiab., S.M. Seyedia Page 1135
    Two novel heterocyclic triazines and tetrazole systems were synthesized through cyclization of 2-hydrazino-furo[2,3-d]pyrimidine with α-haloketones and nitrous acid respectively in high yields. The starting 2-hydrazino-pyrimidine was synthesized from 4-imino-3,6-diphenyl-furo[2,3-d]pyrimidine-2(1H)-thione by methylation and subsequent nucleophilic displacement of methylthio group with hydrazine hydrate.
  • J.J. Wang, J.Z. Li, F.G. Li Page 1139
    An efficient methodology has been developed for the regioselective synthesis of brominated chlorins related to chlorophyll-a from methyl pheophorbide-a. Several regioselective bromination reactions were accomplished by some particular reactionconditions and a series of conversion of functional group from methyl pheophorbide-a to synthesize mono-, bis- and tri-brominated chlorines. The possible mechanisms for the debromination were tentatively proposed and the structures of all new chlorins were characterized by elemental analysis, IR, UV-Vis and 1H NMR spectra.